1. Field of the Invention
The present invention relates to a voltage regulator circuit for a memory circuit, and more particularly, to a voltage regulator circuit having a capacitor for a memory circuit.
2. Description of the Related Art
Voltage regulators are used to regulate voltage levels of a circuit and supply internal power. In memory devices, such as DRAM, many voltage regulators are used, which unavoidably consume a lot of power. To solve such problem, U.S. Pat. No. 6,456,553 discloses a method that turns off the voltage regulators while in standby mode unless a self-refresh in standby mode is requested. Although such method can save power, it is not easy to maintain or immediately generate the voltage level needed for power-up upon a self-refresh request.
US20070001752 and U.S. Pat. No. 7,248,532 disclose another method that reduces the operating voltage in standby mode to 1.5 volts in contrast with 2 volts in active mode. However, because the charge stored in the DRAM cells in standby mode is smaller than the charge needed in active mode, the refresh cycle must be shortened to maintain system operability.
U.S. Pat. No. 6,385,119 discloses one large power voltage-drop regulator and one small power voltage-drop regulator. The large power voltage-drop regulator is turned on while in active mode only. In addition, the small power voltage-drop regulator is always on, including during active, active pause and standby modes. However, the small power voltage-drop regulator still consumes power while in standby mode, and does not perform well upon a self-refresh request.